Method for performing sidelink communication and device therefor

ABSTRACT

The present disclosure relates to a method and device for providing a V2X service in a next generation radio access technology (new RAT). The present embodiments may provide a method and device for performing sidelink communication by a transmission terminal, the method comprising the steps of: receiving, from a base station, one or more pieces of DMRS pattern information and a resource information set comprising information about one or more sidelink resources; selecting, on the basis of the resource information set, one sidelink resource for performing sidelink communication; selecting, on the basis of the selected one sidelink resource, a particular DMRS pattern from among the one or more pieces of DMRS pattern information; and transmitting a PSCCH and a PSSCH in one slot by using the selected sidelink resource, and transmitting, on the basis of the particular DMRS pattern, a DMRS from a particular symbol of the PSSCH.

TECHNICAL FIELD

The present disclosure relates to a method and device for providing avehicle-to-everything (V2X) service in next generation wireless accessnetwork (New RAT).

BACKGROUND ART

There is demand for high-capacity data processing, high-speed dataprocessing, and a variety of services using a wireless terminal invehicles, industrial sites, and the like. In this manner, there isdemand for technology for high-speed and high-capacitytelecommunications systems grown out of simple voice-centric servicesand able to process a variety of scenarios and high-capacity data, suchas images, wireless data, machine-type communication data, and the like.

In this regard, the ITU radiocommunication sector (ITU-R) disclosesrequirements for the adaptation of international mobiletelecommunications-2020 (IMT-2020) international standards. Researchinto next-generation wireless communication technology for meetingIMT-2020 requirements is underway.

In particular, in the 3rd generation partnership project (3GPP),research into LTE-Advanced Pro Rel-15/16 standards and new radio accesstechnology (NR) standards is underway in order to meet IMT-2020requirements referred to as 5G technology requirements. The two standardtechnologies are planned to be approved as next-generation wirelesscommunication technologies.

5G technology may be applied to and used in autonomous vehicles. In thisregard, 5G technology needs to be applied to vehicle-to-everything(V2X). For autonomous driving, it is necessary to transmit and receiveincreasing amounts of data at high speeds with high reliability.

In addition, both unicast data transmission and reception and multicastdata transmission and reception using vehicle communications must beprovided in order to meet driving scenarios, such as platooning, of avariety of autonomous vehicles. In such a situation, there is a demandfor the development of technology able to provide high-reliability datatransmission and reception in vehicle communications.

DISCLOSURE Technical Problem

Embodiments of the present disclosure may provide a method and devicefor performing sidelink communications using next-generation wirelessaccess technology.

Technical Solution

According to an aspect, embodiments of the present disclosure mayprovide a method of performing sidelink communication by a transmittingterminal. The method may include: receiving information regarding one ormore DMRS patterns and a resource information set including informationregarding one or more sidelink resources from a base station; selectinga single sidelink resource for performing sidelink communication inaccordance with the resource information set; selecting a predetermineddemodulation reference signal (DMRS)pattern from the informationregarding one or more DMRS patterns in accordance with the selectedsidelink resource; and transmitting a physical sidelink control channel(PSCCH) and a physical sidelink shared channel (PSSCH) in a single slotusing the selected sidelink resource and transmitting a DMRS in apredetermined symbol of the PSSCH in accordance with the predeterminedDMRS pattern.

According to another aspect, embodiments of the present disclosure mayprovide a method of performing sidelink communication by a receivingterminal. The method may include: receiving information regarding one ormore DMRS patterns and a resource information set including informationregarding one or more sidelink resources from a base station; receivinga PSCCH via a single sidelink resource selected by a transmittingterminal; reviewing scheduling information of a PSSCH and informationregarding a predetermined DMRS pattern received by being included in thePSSCH, in accordance with the PSCCH; and receiving a DMRS in apredetermined symbol of the PSSCH in accordance with the informationregarding a predetermined DMRS pattern.

According to a further aspect, embodiments of the present disclosure mayprovide a transmitting terminal performing sidelink communication, Thetransmitting terminal may include: a receiver receiving informationregarding one or more DMRS patterns and a resource information setincluding information regarding one or more sidelink resources from abase station; a controller selecting a single sidelink resource forperforming sidelink communication in accordance with the resourceinformation set and selecting a predetermined DMRS pattern from theinformation regarding one or more DMRS patterns in accordance with theselected sidelink resource; and a transmitter transmitting a PSCCH and aPSSCH in a single slot using the selected sidelink resource andtransmitting a DMRS in a predetermined symbol of the PSSCH in accordancewith the predetermined DMRS pattern.

ADVANTAGEOUS EFFECTS

According to embodiments of the present disclosure, the method anddevice for performing sidelink communications using next-generationwireless access technology may be provided.

DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram schematically illustrating a structure of an NRwireless communications system to which embodiments are applicable;

FIG. 2 is a diagram illustrating the frame structure in the NR wirelesscommunications system to which embodiments are applicable;

FIG. 3 is a diagram illustrating a resource grid supported by wirelessaccess technology to which embodiments are applicable;

FIG. 4 is a diagram illustrating a bandwidth part supported by wirelessaccess technology to which embodiments are applicable;

FIG. 5 is a diagram illustrating an example synchronization signal blockin wireless access technology to which embodiments are applicable;

FIG. 6 is a diagram illustrating a random access procedure in wirelessaccess technology to which embodiments are applicable;

FIG. 7 is a diagram illustrating a CORESET to which embodiments areapplicable;

FIG. 8 is a diagram illustrating a variety of scenarios for V2Xcommunications;

FIGS. 9a and 9b illustrate an example of terminals (UE1, UE1) performingsidelink communications and an example of a sidelink resource pool usedby the terminals;

FIG. 10 is a diagram illustrating a method of bundling and transmittingHARQ feedback information in a sidelink;

FIG. 11 illustrates a method of performing at least one of activation(request), reactivation (re-request), and release or change of an SPStriggered by the terminal (UE);

FIG. 12 is a diagram illustrating operations of a transmitting terminalaccording to an embodiment;

FIG. 13 is a diagram illustrating operations of a receiving terminalaccording to an embodiment;

FIG. 14 is a diagram illustrating sidelink control information fieldsaccording to an embodiment;

FIG. 15 is a diagram illustrating a pattern in which a PSCCH and a PSSCHare assigned to a single slot and a DMRS is allocated to a variety ofsymbols;

FIGS. 16 to 19 are diagrams illustrating patterns in a variety offrequency domain in which a DMRS is disposed in a predetermined symbolof a PSSCH according to a DMRS pattern;

FIG. 20 is a diagram illustrating a method of determining DMRSallocation symbols according to an embodiment; and

FIG. 21 is a diagram illustrating a configuration of a transmittingterminal according to an embodiment.

BEST MODE

Hereinafter, some embodiments of the present disclosure will bedescribed in detail with reference to the accompanying illustrativedrawings. In designating elements of the drawings by reference numerals,the same elements will be designated by the same reference numeralsalthough being shown in different drawings. Further, in the followingdescription of the present disclosure, detailed descriptions of knownfunctions and configurations incorporated herein will be omitted in thesituation in which the subject matter of the present disclosure may berendered rather unclear thereby. Terms such as “including”, “having”,“containing”, “constituting”, “make up of”, and “formed of” as usedherein are generally intended to allow other components to be addedunless the terms are used with the term “only”. As used herein, singularforms are intended to include plural forms unless the context clearlyindicates otherwise.

In addition, terms, such as first, second, A, B, (a), (b) or the likemay be used herein when describing components of the present disclosure.These terminologies are not used to define an essence, order, sequence,or number of corresponding components but used merely to distinguish thecorresponding components from other components.

In the case that it is described that two or more elements are“connected”, “coupled”, or “linked” to each other, such wording shouldbe interpreted as meaning the two or more elements may not only bedirectly “connected”, “coupled”, or “linked” to each other but also be“connected”, “coupled”, or “linked” to each other via another“intervening” element. Here, the other element may be included in one ormore of the two or more elements “connected”, “coupled”, or “linked” toeach other.

When temporally relative terms, such as “after”, “subsequent to”,“next”, “before”, and the like, are used to describe processes oroperations of elements or configurations, or flows or steps inoperating, processing, or manufacturing methods, these terms may be usedto describe non-consecutive or non-sequential processes or operationsunless the term “directly” or “immediately” is used together.

In addition, when any dimensions, relative sizes, etc. are mentioned, itshould be considered that numerical values for elements or features, orcorresponding information (e.g. level, range, etc.) include a toleranceor error range that may be caused by various factors (e.g. processfactors, internal or external impacts, noise, etc.) even when a relevantdescription is not specified.

The term “wireless communications system” used herein refers to a systemproviding a range of communication services, including voice and packetdata, using radio resources (or wireless resources). Such a wirelesscommunications system may include a terminal (or user equipment), a basestation, a core network, and the like.

Embodiments disclosed hereinafter may be used in wireless communicationssystems using a range of wireless access technologies. For example,embodiments may be used in a range of wireless access technologies, suchas code division multiple access (CDMA), frequency division multipleaccess (FDMA), time division multiple access (TDMA), orthogonalfrequency division multiple access (OFDMA), single carrier frequencydivision multiple access (SC-FDMA), or non-orthogonal multiple access(NOMA). In addition, wireless access technologies may mean not onlyspecific access technologies but also communications technologiesaccording to the generation, established by a variety of communicationsconsultative organizations, such as the 3rd generation partnershipproject (3GPP), the 3rd generation partnership project 2 (3GPP2), theWi-Fi alliance, the Bluetooth, the institute of electrical andelectronics engineers (IEEE), and the international telecommunicationunion (ITU). For example, CDMA may be realized by a wireless technology,such as universal terrestrial radio access (UTRA) or CDMA2000. TDMA maybe realized by a wireless technology, such as the global system formobile communications (GSM), General Packet Radio Service (GPRS), orenhanced data rates for GSM evolution (EDGE). OFDMA may be realized by awireless technology, such as IEEE802.11 (Wi-Fi), IEEE 802.16 (WiMAX),IEEE 802-20, or evolved-UMTS terrestrial radio access (E-UTRA, whereUMTS denotes the universal mobile telecommunications system). IEEE802.16m, evolved from IEEE 802.16e, provides backward compatibility withsystems based on IEEE 802.16e. UTRA is a portion of UMTS. 3rd generationpartnership project (LTE) long term evolution (3GPP) is a portion ofevolved UMTS (E-UMTS) using E-UTRA, and uses OFDMA in downlinks andSC-FDMA in uplinks. In this manner, embodiments of the presentdisclosure may be used in wireless access technologies that arecurrently disclosed or commercially available, or may be used in anywireless access technology currently being, or which will be, developed.

In addition, the term “terminal” used herein should be interpreted ashaving a comprehensive term referring to a wireless communicationsmodule that communicates with a base station in a wirelesscommunications system, and should be interpreted as including not only aterminal in WCDMA, LTE, NR, HSPA, IMT-2020 (5G or New Radio), and thelike, but also all of a mobile station (MS), a user terminal (UT), asubscriber station (SS), a wireless device, and the like, used in GSM.In addition, the terminal may refer to a user mobile device, such as asmartphone, depending on the type of use or may refer to a vehicle or adevice including a wireless communications module in the vehicle in thevehicle-to-everything (V2X) communications system. Furthermore, in themachine type communications (MTC) system, the terminal may refer to anMTC terminal, a machine-to-machine (M2M) terminal, an ultra-reliabilityand low latency communications (URLLC)terminal, or the like, providedwith a communications module able to perform machine typecommunications.

The term “base station” or “cell” used herein refers to an end in anetwork, communicating with the terminal, and comprehensively indicatesa variety of coverage areas, such as a node-B, an evolved node-B (eNB),a gNodeB (gNB), a low power node (LPN), a sector, a site, an antennahaving a variety of shapes, a base transceiver system (BTS), an accesspoint, a point (e.g. a communication point, a reception point, or atransmission/reception point), a relay node, a megacell, a macrocell, amicrocell, a picocell, a femtocell, a remote radio head (RRH), a radiounit (RU), and a small cell. In addition, the cell may be understood asincluding a bandwidth part (BWP) in a frequency domain. For example, aserving cell may refer to an activation BWP of the terminal.

Since at least one of the variety of cells as stated above is controlledby a dedicated base station, the base station may be interpreted in twosenses. Each of the base stations 1) may be an apparatus itselfproviding a megacell, a macrocell, a microcell, a picocell, a femtocell,or a small cell in relation to a wireless communication area, or 2) mayindicate the wireless communication area itself. In 1), when apparatusesproviding wireless areas are controlled by the same entity orapparatuses interact with one another to form a wireless area in acoordinated manner, all of such apparatuses may be referred to as basestations. The transmission/reception point, the transmission point, thereception point, and the like are examples of the base station,according to the configuration of the wireless area. In 2), the wirelessarea itself in which a signal is received or transmitted may be referredto as a base station, from the perspective of a user or an adjacent basestation.

The term “cell” used herein may refer to a coverage of a signaltransmitted from the transmission point or the transmission/receptionpoint, a component carrier having the coverage of the signal transmittedfrom transmission point or the transmission/reception point, or thetransmission point or the transmission/reception point.

Here, the term “uplink (UL)” refers to a data transmission/receptionmethod by which data is transmitted from the terminal to the basestation, whereas the term “downlink (DL)” refers to a datatransmission/reception method by which data is transmitted from the basestation to the terminal. The downlink may refer to communications or acommunication path from a multiple transmission/reception point to theterminal, whereas the uplink may refer to communications or acommunication path from the terminal to the multipletransmission/reception point. In the downlink, a transmitter may be aportion of the multiple transmission/reception point, whereas a receivermay be a portion of the terminal. In addition, in the uplink, thetransmitter may be a portion of the terminal, whereas the receiver maybe a portion of the multiple transmission/reception point.

The uplink and the downlink transmit and receive control information viaa control channel, such as a physical downlink control channel (PDCCH)or a physical uplink control channel (PUCCH), and transmit and receivedata by forming a data channel, such as a physical downlink sharedchannel (PDSCH) or a physical uplink shared channel (PUSCH).Hereinafter, transmitting or receiving a signal via a channel, such asthe PUCCH, the PUSCH, the PDCCH, or the PDSCH, may also be described as“transmitting or receiving the PUCCH, the PUSCH, the PDCCH, or thePDSCH”.

To clarify the description, the principle of the present disclosure willbe described with respect to 3GPP LTE/LTE-A/NR (New RAT) communicationssystem but the technical features of the present disclosure are notlimited to the corresponding communications system.

In 3GPP, 5th generation (5G) communications technology for meetingrequirements for next generation wireless access technology of theinternational telecommunication union radiocommunication sector (ITU-R)is developed. Specifically, in 3GPP, research on new NR communicationstechnology separate from LTE advanced Pro (LTE-A Pro) and 4Gtelecommunications technology improved from LTE Advanced in accordancewith the requirements of the ITU-R is developed. Both LTE-A Pro and NRrefer to 5G communications technology. Hereinafter, 5G communicationstechnology will be described with respect to NR, except that aparticular communications technology is specified.

In NR, a variety of operation scenarios are defined by addingconsiderations regarding satellites, vehicles, new vertical services,and the like to in typical 4G LTE scenarios. In terms of services, NRsupports an enhanced mobile broadband (eMBB) scenario; a massive machinecommunication (MMTC) scenario having high terminal density, deployedover a wide range, and requiring low data rates and asynchronousaccesses; and an ultra-reliability and low latency communications(URLLC) scenario requiring high responsiveness and reliability and ableto support high-speed mobility.

In order to meet the scenario described above, NR discloses a wirelesscommunications system using technologies providing a new waveform andframe structure, providing a low latency, supporting ultrahigh frequencywaves (mmWave), and providing forward compatibility. In particular, theNR system presents various technical changes in terms of flexibility inorder to provide forward compatibility. Major technical features of NRwill be described hereinafter with reference to the drawings.

<Principle of NR System>

FIG. 1 is a diagram schematically illustrating a structure of an NRwireless communications system to which embodiments of the presentdisclosure are applicable.

Referring to FIG. 1, the NR system is divided into a 5G core network(5GC) part and an NR-RAN part. The NG-RAN includes gNBs and ng-eNBsproviding protocol ends of a user plane (SDAP/PDCP/RLC/MAC/PHY) and acontrol plane (or a radio resource control (RRC)) for user equipment UE(or terminal). The gNBs are connected to each other, or the gNBs and theng-eNBs are connected to each other via an Xn interface. The gNBs andthe ng-eNBs are connected to each other via an NG interface in the 5GC.The 5GC may include an access and mobility management function (AMF)managing a control plane, such as terminal access and mobility control,and a user plane function (UPF) managing a control function over userdata. The NR system supports both a frequency range of 6 GHz or lower,i.e. frequency range 1 (FR1), and a frequency range of 6 GHz or higher,i.e. frequency range 2 (FR2).

The gNBs refer to base stations providing the NR user plane and controlplane protocol ends to the terminal, whereas the ng-eNBs refer to basestations providing evolved UMTS (E-UTRA) user plane and control planeprotocol ends to the terminal. The term “base station” used hereinshould be understood as comprehensively indicating the gNB and theng-eNB, or may be used as separately indicating the gNB and the ng-eNBas required.

<NR Waveform, Numerology, and Frame Structure>

In NR, cyclic prefix orthogonal frequency-division multiplexing(CP-OFDM) waveforms using the cyclic prefix (CP) for downlinktransmissions are used, and CP-OFDM or discrete Fourier transform spread(DFT-s)-OFDM is used for uplink transmissions. The OFDM technology hasadvantages in that the OFDM technology may be easily combined with amultiple-input multiple-output (MIMO) method, may have a high frequencyefficiency, and may use a low-complexity receiver.

In addition, in NR, requirements for data rate, latency, coverage, andthe like are different according to the above-described three scenarios.Thus, it is necessary to efficiently meet the requirements according tothe scenarios through frequency ranges of the NR system. In this regard,a technology for efficiently multiplexing a plurality of differentnumerology-based radio resources has been proposed.

Specifically, NR transmission numerology is determined on the basis ofsubcarrier spacing and the cyclic prefix (CP), and μ values areexponential values of 2 on the basis of 15 kHz and are exponentiallychanged, as described in Table 1 below.

TABLE 1 Subcarrier Cyclic Supported Supported μ Spacing Prefix for Datafor Synch 0 15 Normal Yes Yes 1 30 Normal Yes Yes 2 60 Normal, Yes NoExtended 3 120 Normal Yes Yes 4 240 Normal No Yes

As described in Table 1 above, the numerology of NR may be divided intofive types according to the subcarrier spacing. This differs from thefeature of LTE, i.e. one of 4G communications technologies, in which thesubcarrier spacing is fixed to 15 kHz. Specifically, in NR, thesubcarrier spacings used for data transmissions are 15, 30, 60, and 120kHz, and the subcarrier spacings used for synchronous signaltransmissions are 15, 30, 12, and 240 kHz. In addition, an extended CPis only applied to 60 kHz subcarrier spacing. On the other hand, theframe structure in NR is defined as a frame having a length of 10 mscomprised of 10 subframes having the same lengths of 10 ms. A singleframe may be divided into 5 ms half frames, each of which includes fivesubframes. In the case of 15 kHz subcarrier spacing, a single subframecomprises a single slot, and each slot comprises fourteen OFDM symbols.

FIG. 2 is a diagram illustrating the frame structure in the NR system towhich embodiments of the present disclosure are applicable.

Referring to FIG. 2, the slot is constantly comprised of 14 OFDM symbolsin the case of a normal CP, but the length of the slot in the timedomain may vary depending on the subcarrier spacing. For example, whenthe numerology has the 15 kHz subcarrier spacing, the length of the slotis 1 ms, identical to that of the subframe. Differently thereto, whenthe numerology has the 30 kHz subcarrier spacing, the slot may becomprised of 14 OFDM symbols and have 0.5 ms length, such that two slotsmay be included in a single subframe. That is, each of the subframe andthe frame is defined having a fixed time length, and the slot may bedefined by the number of symbols, such that the time length may varydepending on the subcarrier spacing.

In addition, in NR, the slot is defined as a basic unit of thescheduling, and a mini-slot (or a sub-slot or a non-slot based schedule)is introduced in order to reduce a transmission delay in a wirelesssection. When a wide subcarrier spacing is used, the transmission delayin the wireless section may be reduced, since the length of a singleslot is shortened in inverse proportion thereto. The mini-slot (orsub-slot) is devised to efficiently support URLLC scenarios andscheduling on the basis of 2, 4, or 7 symbols may be possible.

In addition, unlike LTE, NR defines uplink and downlink resourceallocations as symbol levels in a single slot. In order to reduce hybridautomatic repeat request (HARQ) latency, a slot structure able todirectly transmit at least one of an HARQ acknowledgement (HARQACK)or anHARQ negative acknowledgement (HARQNACK) in a transmission slot isdefined. In the description, this slot structure will be referred to asa self-contained structure.

NR is designed to support a total of 256 slot formats, of which 62 slotformats are used in 3GPP Rel-15. In addition, various slot combinationssupport a common frame structure including an FDD, or a TDD frame. Forexample, NR supports a slot structure in which all symbols of the slotare configured as downlinks, a slot structure in which all symbols ofthe slot are configured as uplinks, and a slot structure in whichdownlink symbols and uplink symbols are combined. In addition, NRsupports a form of scheduling in which data transmission is distributedin one or more slots. Accordingly, the base station may inform theterminal of whether a corresponding slot is a downlink slot, an uplinkslot, or a flexible slot, using a slot format indicator (SFI).The basestation may indicate a slot format by indicating an index of a table,configured by terminal-specific (UE-specific) RRC signaling, using theSFI, dynamically using downlink control information(DCI), or staticallyor quasi-statically through the RRC.

<NR Physical Resource>

Regarding the physical resources in NR, antenna ports, resource grids,resource elements (RE), resource blocks, bandwidth parts (BWPs), and thelike are considered.

The term “antenna port” is defined such that a channel carrying a symbolon an antenna port may be inferred from a channel carrying anothersymbol on the same antenna port. When the large-scale property of achannel carrying the symbol on one antenna port is inferable from achannel carrying a symbol on another antenna port, the two antenna portsmay be in a quasi co-located or quasi co-location (QC/QCL) relationship.Here, the large-scale property includes at least one of a delay spread,a Doppler spread, a frequency shift, average received power, andreceived timing.

FIG. 3 is a diagram illustrating a resource grid supported by wirelessaccess technology to which embodiments of the present disclosure areapplicable.

Referring to FIG. 3, since NR supports a plurality of numerologies inthe same carrier, the resource grid maybe present according to eachnumerology. In addition, the resource grid may be configured dependingon the antenna port, the subcarrier spacing, and the transmissiondirection.

A resource block is comprised of 12 subcarriers and is only defined in afrequency domain. In addition, a resource element is comprised of oneOFDM symbol and one subcarrier. Therefore, as shown in FIG. 3, the sizeof one resource block may vary depending on the subcarrier spacing. Inaddition, NR defines “point A” serving as a common reference point for aresource block grid, a common resource block, and a virtual resourceblock.

FIG. 4 is a diagram illustrating a BWP supported by wireless accesstechnology to which embodiments of the present disclosure areapplicable.

In the NR, the maximum carrier bandwidth is configured to be in therange from 50 MHz to 400 MHz depending on the subcarrier spacing, unlikein the LTE with the carrier bandwidth thereof being fixed to 20 MHz.Thus, it is not assumed that all terminals use all of these carrierbandwidths. Accordingly, as illustrated in FIG. 4, in NR, a bandwidthpart (BWP) may be designated within a carrier bandwidth so as to be usedby the terminal. In addition, the BWP may be associated with onenumerology, be comprised of a contiguous subset of the common resourceblocks, and be dynamically activated over time. The terminal is providedwith up to four BWPs in each of an uplink and a downlink, and transmitsand receives data using an activated BWP at a given time.

In the case of a paired spectrum, the uplink and downlink BWPs areconfigured independently. In the case of an unpaired spectrum, theuplink BWP and the downlink BWP are configured in pairs such that thecenter frequency may be shared therebetween in order to preventunnecessary frequency re-tuning between downlink and uplink operations.

<Initial Access of NR>

In NR, the terminal performs cell search and random access procedures toaccess a base station and performs communications with the base station.

The cell search procedure is a procedure of synchronizing the terminalwith the cell of a corresponding base station using asynchronizationsignal block (SSB) transmitted from the base station, acquiring aphysical layer cell identifier (ID), and acquiring system information.

FIG. 5 is a diagram illustrating an example synchronization signal blockin wireless access technology to which embodiments of the presentdisclosure are applicable.

Referring to FIG. 5, an SSB includes a primary synchronization signal(PSS) and a secondary synchronization signal (SSS), each of whichoccupies one symbol and 127 subcarriers, and a physical broadcastchannel (PBCH)covering three OFDM symbols and 240 subcarriers.

The terminal receives the SSB by monitoring the SSB in time andfrequency domains.

The SSB may be transmitted up to 64 times for 5 ms. A plurality of SSBsare transmitted on different transmission beams within a period of 5 ms,and the terminal performs detection on the assumption that an SSB istransmitted at every 20 ms period, on the basis of a specific beam usedfor transmission. The number of beams that may be used for the SSBtransmission within the 5 ms period may increase with increases in thefrequency range. For example, up to four SSB beams may be transmitted ina frequency range of 3 GHz or lower. SSB may be transmitted using up toeight beams in a frequency range of 3 to 6 GHz and up to 64 differentbeams in a frequency range of 6 GHz or higher.

Two SSBs are included in one slot, and the start symbol and the numberof repetitions in the slot are determined depending on the subcarrierspacing as will be described below.

In addition, unlike an SS of related-art LTE, the SSB is not transmittedat the center frequency of a carrier bandwidth. That is, the SSB may betransmitted on a frequency that is not the center frequency of a systemrange, and a plurality of SSBs maybe transmitted in a frequency domainwhen a wideband operation is supported. Thus, the terminal monitors theSSBs using a synchronization raster that is a candidate frequencyposition for the monitoring of the SSBs. A carrier raster and thesynchronous raster, which are center frequency position information of achannel for initial access, are newly defined in NR. The synchronousraster is configured to have a wider frequency interval than the carrierraster, and thus, may support the terminal for rapid SSB search.

The terminal may acquire a master information block (MIB) through thePBCH of the SSB. The MIB includes minimum information by which theterminal receives remaining minimum system information (RMSI) broadcastby the network. In addition, the PBCH may include information regardingthe position of a first demodulation reference signal (DM-RS) symbol inthe time domain, information (e.g. system information block 1 (SIB1)numerology information, information regarding an SIB1 control resourceset (SIB1 CORESET), search space information, or PDCCH related parameterinformation) by which the terminal monitors SIB1, information regardingan offset between a common resource block and an SSB(where the absoluteposition of the SSB in the carrier is transmitted via SIB1), and thelike. Here, the SIB1 numerology information is equally applied to somemessages used in a random access procedure for accessing a base stationafter the terminal has completed the cell search procedure. For example,the SIB1 numerology information may be applied to at least one ofmessages 1 to 4 for the random access procedure.

The above-described RMSI may refer to system information block 1 (SIB1),which is periodically broadcast (e.g. at 160 ms)in the cell. SIB1includes information necessary for the terminal to perform an initialrandom access procedure and is periodically transmitted through thePDSCH. In order for the terminal to receive SIB 1, the terminal isrequired to receive numerology information, which is used for SIB1transmission, and control resource set (CORESET) information, which isused for SIB1 scheduling, through the PBCH. The terminal checksscheduling information regarding SIB1 using a system information radionetwork temporary identifier (SI-RNTI) in the CORESET, and acquires SIB1on the PDSCH according to the scheduling information. The remaining SIBsother than SIB1 may be periodically transmitted or may be transmitted atthe request of the terminal.

FIG. 6 is a diagram illustrating a random access procedure in wirelessaccess technology to which embodiments of the present disclosure areapplicable.

Referring to FIG. 6, when cell search is completed, the terminaltransmits a random access preamble, in use for random access, to thebase station. The random access preamble is transmitted through aphysical random access channel (PRACH). Specifically, the random accesspreamble is transmitted to the base station through the PRACH comprisedof consecutive radio resources in a predetermined slot periodicallyrepeated. In general, a contention-based random access procedure isperformed when terminal initially accesses a cell, whereas anon-contention based random access procedure is performed when randomaccess is performed for beam failure recovery (BFR).

The terminal receives a random access response to the transmitted randomaccess preamble. The random access response may include a random accesspreamble identifier (ID), an uplink (UL) radio resource grant, atemporary cell radio network temporary ID (temporary C-RNTI), and a timealignment command (TAC).Since one random access response may includerandom access response information regarding one or more sets ofterminal, the random access preamble ID may be included to order toindicate to which terminal the included UL grant, the temporary C-RNTI,and the TAC are valid. The random access preamble ID may be an ID of therandom access preamble that the base station has received. The TAC maybe included as information by which the terminal adjusts uplinksynchronization. The random access response may be indicated by a randomaccess ID on the PDCCH, i.e., a random access-radio network temporary ID(RA-RNTI).

When the valid random access response is received, the terminalprocesses information included in the random access response andperforms a scheduled transmission to the base station. For example, theterminal applies the TAC and stores the temporary C-RNTI. In addition,the terminal transmits data stored in a buffer or newly generated datato the base station, using the UL grant. In this case, information bywhich the terminal may be identified must be included.

Finally, the RA-RNTI receives a downlink message for contentionresolution.

<NR CORESET>

In NR, a downlink control channel is transmitted on a control resourceset (CORESET) having a length of 1 to 3 symbols. Up/down schedulinginformation, slot format index (SFI) information, transmit power controlinformation, and the like are transmitted through the downlink controlchannel.

Thus, in NR, in order to secure the flexibility of the system, theCORESET is introduced. The control resource set (CORESET) refers to atime-frequency resource for a downlink control signal. The terminal maydecode a control channel candidate using one or more search spaces in aCORESET time-frequency resource. Quasi colocation (QCL) assumption isestablished according to the CORESET. The QCL assumption is used inorder to inform the characteristics of analogue beam directions inaddition to characteristics assumed by related-art QCL, such as adelayed spread, a Doppler spread, a Doppler shift, or an average delay.

FIG. 7 is a diagram illustrating a CORESET.

Referring to FIG. 7, the CORESET may have a variety of forms within acarrier bandwidth in a single slot. The CORESET may be comprised of upto three OFDM symbols in the time domain. In addition, the CORESET isdefined as a multiple of six resource blocks up to the carrier bandwidthin the frequency domain.

The first CORESET is a portion of an initial BWP configuration,indicated through the MIB so as to be able to receive additionalconfiguration information and system information from the network. Aftera connection to the base station is established, the terminal mayreceive and configure one or more pieces of CORESET information throughRRC signaling.

Herein, terms, such as frequency, frame, subframe, resource, resourceblock, region, band, sub-band, control channel, data channel,synchronization signal, various reference signals, various signals, orvarious messages, related to new radio access technology (NR) may beinterpreted as having a variety of meanings related to concepts used inthe past or present or which will be used in the future.

<Sidelink>

In existing LTE systems, wireless channels and wireless protocols havebeen designed for direct (i.e. sidelink) communications betweenterminals in order to provide direct terminal-to-terminal communicationsand V2X (in particular, V2V) services.

Regarding the sidelink, synchronization signals, e.g. a sidelink primarysynchronization signal (S-PSS) and a sideline secondary synchronizationsignal (S-SSS), for synchronization between a transmission port and areceiver port of the wireless sidelink and a physical sidelinkbroadcasting channel (PSBCH) for the transmission and reception of arelated sidelink master information block (MIB) are defined. Inaddition, a physical sidelink discovery channel (PSDCH) for transmissionand reception of discovery information, a physical sidelink controlchannel (PSCCH) for transmission and reception of sidelink controlinformation (SCI), and a physical sidelink shared channel (PSSCH) fortransmission and reception of sidelink data are designed.

In addition, technological developments, made for wireless resourceallocation (or radio resource allocation) for the sidelink, have beendivided into Mode 1, in which the base station allocates wirelessresources and Mode 2, in which the terminal performs allocation byselecting a wireless resource pool. In addition, the LTE system requiresadditional technological evolution in order to meet V2X scenarios.

In this environment, the 3GPP has deduced 27 service scenarios relatedto the recognition of a vehicle in the Rel-14 and determined majorperformance requirements according to road situations.

In addition, in the Rel-15, six performance requirements are determinedby deducing more advanced 25 service scenarios, such as platooning,advanced driving, and long-distance vehicle sensing.

In order to meet such performance requirements, technical developmenthas been carried out to improve the performance of conventional sidelinktechnology developed on the basis of D2D communications to comply withthe V2X requirements. In particular, for application to the cellular-V2X(C-V2X), a technology for improving a physical sidelink layer design tocomply with a high-speed environment, a resource allocation technology,and a synchronization technology may be selected as major researchtechnologies.

The sidelink to be described hereinafter may be construed ascomprehensively including links used in D2D communications developedafter 3GPP Rel-12, V2Xcommunications after the Rel-14, and the NR V2Xafter the Rel-15. In addition, respective terms related to channels,synchronization, resources, and the like will be described as being thesame terms irrespective of the D2D communications requirements or theV2X Rel-14/15 requirements. However, for a better understanding,features of the sidelink meeting the V2X scenario requirements,different from the sidelink for D2D communications in the Rel-12/13,will mainly be described. Therefore, the terms related to the sidelinkto be described hereinafter are merely intended to describe D2Dcommunications, V2Xcommunications, and C-V2Xcommunications in adiscriminative manner in order to compare differences thereof and assistin the understanding thereof, but are not applied to a specific scenarioin a limitative manner.

<Resource Allocation>

FIG. 8 is a diagram illustrating a variety of scenarios forV2Xcommunications.

Referring to FIG. 8, V2X terminals may be located inside or outside ofthe coverage of a base station eNB (or gNB or ng-eNB). (Although the V2Xterminals are illustrated as being vehicles, the V2X terminals may be avariety of devices, such as a user terminal.) For example,communications may be performed between terminals (UE N-1, UE G-1, andUE X) inside the coverage of the base station (or base station coverage)or between a terminal (e.g. UE G-1) inside the base station coverage anda terminal (e.g. UE N-2) outside of the base station coverage. Inaddition, communications may be performed between terminals (e.g. UE G-1and UE G-2) outside of the base station coverage.

In such a variety of scenarios, the allocation of wireless resources forcommunications is required so that the corresponding terminal performssidelink communications. The allocation of wireless resources isgenerally divided into an allocation method handled by the base stationand an allocation method selected by the terminal.

Specifically, the method in which the terminal allocates resources inthe sidelink includes a method in which the base station intervenes inthe selection and management of resources (Mode 1) and a method in whichthe terminal directly selects resources (Mode 2). In Mode 1, the basestation performs scheduling of a transmitting terminal about ascheduling assignment (SA) pool resource domain and a DATA pool resourcedomain allocated thereto.

FIGS. 9a and 9b illustrate an example of terminals UE1 and UE1performing sidelink communications and an example of a sidelink resourcepool used by the terminals.

Referring to FIGS. 9a and 9b , a base station is illustrated as being aneNB, but may be a gNB or an ng-eNB. In addition, the terminals areillustrated as being cellular phones, but may be applied to a variety ofdevices, such as a vehicle or an infrastructure device.

In FIG. 9a , the transmitting terminal UE1 may select a resource unitcorresponding to a predetermined resource from a resource poolindicating a set of resources and transmit a sidelink signal using thecorresponding resource unit. The receiving terminal UE2 may have theresource pool, which the transmitting terminal UE1 may transmit,configured therein and detect the signal transmitted by the transmittingterminal.

Here, when the terminal UE1 is inside the base station coverage, theresource pool may be informed by the base station. When the terminal UE1is outside of the base station coverage, the resource pool may beinformed by another terminal or may be determined to be a predeterminedresource. In general, the resource pool is comprised of a plurality ofresource units, and each terminal may select one or more resource unitsand use the selected resource units when transmitting sidelink signals.

Referring to FIG. 9b , it may be appreciated that a total of NFXNTnumber of resource units are defined, with entire frequency resourcesbeing divided into NF number of frequency resource units, and timeresources being divided into NT number of time resource units. Here, thecorresponding resource pool may be regarded as being repeated in aperiod of an NT subframe. In particular, as illustrated in the figures,a single resource unit may repeatedly appear in a periodic manner.

In addition, the resource pools may be divided into a plurality oftypes. First, the resource pools may be divided according to contents ofsidelink signals transmitted by respective resource pools. For example,the contents of the sidelink signals may be divided, and separateresource pools may be configured therefor, respectively. The contents ofthe sidelink signals may include scheduling assignment (SA), a sidelinkdata channel, and a discovery channel.

The SA may be a signal including information regarding the position of asource that the transmitting terminal uses for the transmission of asubsequent sidelink data channel, a modulation and coding scheme (MCS)or multiple-input multiple-output (MIMO) transmission method requiredfor the modulation of other data channels, timing advance (TA), and thelike. This signal may be multiplexed and transmitted together withsidelink data on the same resource unit. In this case, the SA resourcepool may refer to a pool of resources via which the SA is multiplexedand transmitted together with sidelink data.

In addition, a frequency division multiplexing (FDM) method used inV2Xcommunications may reduce a delay time by which a data resource isapplied after SA resource allocation. For example, a non-adjacent methodby which control channel resources and data channel resources aredivided on the time domain in a single subframe and an adjacent methodby which control channel resources and data channel resources arecontinuously allocated in a single subframe are considered.

In addition, in a case in which the SA is multiplexed and transmittedtogether with the sidelink data on the same resource unit, only thesidelink data channel, from which SA information is excluded, may betransmitted in the resource pool for the sidelink data channel. In otherwords, resource elements that have been used to transmit the SAinformation on individual resource units in the SA resource pool maystill be used in the sidelink data channel resource pool to transmit thesidelink data. The discovery channel may be a resource pool for amessage with which the transmitting terminal transmits information, suchas the ID thereof, thereby allowing an adjacent terminal to discover thetransmitting terminal. Even in a case in which the contents of thesidelink signal are the same, different resource pools may be usedaccording to transmission and reception properties of the sidelinksignal.

For example, even the same sidelink data channels or the same discoverymessages may be subdivided into different resource pools, according tohow to determine a point in time at which the sidelink signal istransmitted (e.g. whether the sidelink signal is transmitted at a pointin time at which a synchronization reference signal is received or at apoint in time obtained by applying a predetermined TA to the point intime at which the synchronization reference signal is received), aresource allocation method (e.g. whether the base station designatestransmission resources of individual signals to individual transmittingterminals or individual transmitting terminals directly selectindividual signal transmission resources within the pool), a signalformat (e.g. the number of symbols that each sidelink signal occupies ina single subframe or the number of subframes used in the transmission ofa single sidelink signal), the intensity of a signal from the basestation, the intensity of transmission power of the sidelink terminal,and the like.

<Synchronization Signal>

As described above, it is highly possible that the sidelinkcommunications terminal may be located outside of the base stationcoverage. Even in this case, communications using the sidelink must beperformed. In this regard, it is important that the terminal locatedoutside of the base station coverage obtains synchronization.

Hereinafter, a method of determining time and frequency synchronizationin sidelink communications, in particular, vehicle-to-vehiclecommunications, communications between a vehicle and another terminal,and communications between a vehicle and an infranet work, will bedescribed on the basis of the above description.

D2Dcommunications have used a sidelink synchronization signal (SLSS),i.e. a synchronization signal that a base station transmits for timesynchronization between terminals. In the C-V2X, the global navigationsatellite system (GNSS) may be additionally considered in order toimprove synchronization performance. However, priority may be impartedto synchronization establishment, or the base station may indicateinformation regarding priority. For example, when the terminaldetermines the transmission synchronization thereof, the terminal hashighest priority in selecting a synchronization signal that the basestation directly transmits. When the terminal is located outside of thebase station coverage, the terminal has priority in synchronization withthe SLSS that a terminal inside the base station coverage.

In addition, a wireless terminal disposed in a vehicle or a terminalmounted on a vehicle has a less problem related to the consumption ofthe battery. In addition, since satellite signals, e.g. signals of theglobal positioning system (GPS), may be used for navigation, thesatellite signals may be used for time or frequency synchronizationbetween terminals. Here, the satellite signals may be signals of aglobal navigation satellite system (GNSS), such as GLONAS, GALILEO, orBEIDOU, in addition to the GPS.

In addition, the sidelink synchronization signals may include a sidelinkprimary synchronization signal (S-PSS) and a sideline secondarysynchronization signal (S-SSS). The S-PSS may be a Zadoff-chu sequencehaving a predetermined length, a structure similar to, modified from, orobtained by repeating the PSS, or the like. In addition, unlike a DLPSS, a different Zadoff-chu root index (e.g. 26 or 37) may be used. TheS-SSS may be an M-sequence, a structure similar to, modified from, orobtained by repeating the SSS, or the like. If the terminals obtainsynchronization with the base station, an SRN is the base station, and asidelink synchronization signal (S-SS) is a PSS/SSS.

Unlike the DL PSS/SSS, the S-PSS/S-SSS is compliant with a UL subcarriermapping method. A physical sidelink broadcast channel (PSBCH) may be achannel through which system information, i.e. basic information that isthe first thing which the terminal must be informed of, is transmittedbefore the transmission or reception of the sidelink signal. (Examplesof the system information may include information regarding the S-SS,information regarding a duplex mode (DM), information regarding a TDDUL/DL configuration, information regarding the resource pool, types ofapplications related to the S-SS, subframe offset information, andbroadcast information.) The PSBCH may be transmitted on a subframe thesame as or subsequent to that of the S-SS. A demodulation referencesignal (DMRS) may be mused for the demodulation of the PSBCH. The S-SSand the PSBCH may be described as being a sidelink synchronizationsignal block (S-SSB).

The SRN may be a node through which the S-SS and the PSBCH aretransmitted. The S-SS may have a predetermined sequence type, while thePSBCH may be a sequence indicating predetermined information or a codeword obtained after predetermined channel coding. Here, the SRN may bethe base station or a predetermined sidelink terminal. In the case of apartial network coverage or out-of-network coverage, a terminal may bethe SRN.

In addition, the S-SS may be relayed for sidelink communications with anout-of-coverage terminal as required or may be relayed by multi-hoprelay. In the following description, relaying the synchronization signalrefers to not only directly relaying the synchronization signal of thebase station but also transmitting a sidelink synchronization signalhaving a separate format at a point in time at which the synchronizationsignal is received. Since the sidelink synchronization signal is relayedin this manner, a terminal inside the coverage and a terminal outside ofthe coverage may directly communicate with each other.

<NR sidelink>

As described above, there is a demand for V2X technology based on NR inorder to meet complicated requirements such as autonomous driving,unlike the V2X based on the LTE system.

In the NR V2X, the frame structure of NR, a numerology, a channeltransmission and reception procedure, and the like are applied so thatmore flexible V2X services may be provided in a more variety ofenvironments. In this regard, the development of a technology forsharing resources between the base station and the terminal, a sidelinkcarrier aggregation (CA) technology, a partial sensing technology for apedestrian terminal, sTTI, and the like is required.

The NR V2X is designed to support not only broadcast used in the LTEV2X, but also unicast and group-cast. In this case, target group IDs areused for the group-cast and the unicast, but whether or not to use asource ID will be discussed later.

In addition, since the HARQ is supported for quality of service (QoS),the control information further includes an HARQ process ID. In the LTEHARQ, the PUCCH for the HARQ is transmitted after four subframes afterdownlink transmission. In contrast, in the NR HARQ, feedback timing,e.g. PUCCH resources and feedback timing, may be indicated using a PUCCHresource indicator or an HARQ feedback timing indicator regarding thePDSCH in DCI format 1_0 or 1_1.

FIG. 10 is a diagram illustrating a method of bundling and transmittingHARQ feedback information in a sidelink.

Referring to FIG. 10, in the LTE V2X, separate HARQ ACK/NACK informationis not transmitted in order to reduce system overhead. In addition,according to selection, the transmitting terminal may retransmit dataone time for data transmission reliability. However, the NR V2X maytransmit the HARQ ACK/NACK information in terms of data transmissionreliability. In this case, the corresponding information may be bundledand transmitted in order to reduce overhead.

That is, when the transmitting terminal UE1 transmits three sets of datato the receiving terminal UE2 and the receiving terminal responsivelygenerates HARQ ACK/NACK information, the HARQ ACK/NACK information maybe bundled and transmitted through the PSCCH. Although the HARA ACK/NACKis illustrated as being transmitted through the PSCCH in FIG. 10, theHARA ACK/NACK may be transmitted through a separate channel or adifferent channel. The bundled HARQ information may be configured to be3 or less bits.

In addition, in FR1 for a frequency domain of 3 GHz or lower, 15 kHz, 30kHz, 60 kHz, and 120 kHz are determined to be discussed as a candidategroup for subscriber spacing (SCS). In addition, in FR2 for a frequencydomain higher than 3 GHz, 30 kHz, 60 kHz, 120 kHz, and 240 kHz aredetermined to be discussed as a candidate group for the SCS. In the NRV2X, mini-slots (e.g. symbols 2, 4, and 7) smaller than 14 symbols maybe supported as a minimum scheduling unit.

As an RS candidate group, DM-RS, PT-RS, CSI-RS, SRS, and AGC trainingsignals will be discussed.

Sidelink UL SPS

In general, UL transmissions using SPS may cause a slight delay whenthere is a significant gap between the generation of user data and aconfigured SPS resource. Thus, when the SPS is used in a traffic, suchas a sidelink communication traffic, sensitive to a delay, an SPSscheduling interval must be small enough to be able to support delayrequirements.

However, since the terminal UE may not be able to sufficiently use theconfigured SPS resource, a smaller SPS scheduling interval may lead togreater overhead. Thus, the gap between the generation of user data andthe configured SPS resource must be insignificant, and the SPSscheduling interval must be appropriate to meet delay requirements. Atpresent, there is no mechanism supporting this function.

Accordingly, FIG. 11 illustrates a method of performing at least one ofactivation (request), reactivation (re-request), and release or changeof an SPS triggered by the terminal UE.

A terminal UE may receive an SPS configuration for at least onepredetermined logic channel. The terminal UE may receive the SPSconfiguration for the predetermined logic channel via systeminformation, an RRC connection configuration message, an RRC connectionreconfiguration message, or an RRC connection release message.

When data for at least one predetermined logic channel is usable, theterminal may transmit an SPS activation request to an eNB and perform ULtransmission using the configured SPS resource in response to an SPSactivation command received from the eNB. The terminal UE may transmitthe SPS activation request to the eNB through a physical uplink controlchannel (PUCCH), a MAC control element (CE), or an RRC message. That is,the terminal may transmit the SPS activation request to the eNB using acontrol resource used when requesting SPS activation. The controlresource may be a PUCCH resource, a random access resource, or a new ULcontrol channel resource. In addition, the terminal UE may transmit theSPS activation request to the eNB, for example, during RRC connectionestablishment or establishment, during handover, after handover, or atRRC_CONNECTED.

In the presence of UL data to be transmitted, the terminal UE activelyrequests the SPS activation from the eNB. Thus, the gap between thegeneration of the UL data and the configured SPS resource may bereduced.

Referring to FIG. 11, the terminal receives SPS configurationinformation including three SPS configurations from the eNB. In thepresence of UL data to be transmitted from a higher layer, the terminaltransmits an SPS request message to the eNB through, for example, theMAC CE. The eNB sends an acknowledgement (ACK) message regarding one ofthe three SPS configurations. The terminal UE transmits UL data based ona predetermined resource, e.g. in a period of 1 sec, according to thecorresponding SPS configuration.

In addition, in the presence of UL data to be transmitted from thehigher layer at a predetermined point in time, the terminal UEretransmits the SPS request message to the eNB, for example, through theMAC CE. The eNB sends an acknowledgement message regarding another oneof the three SPS configurations. The terminal UE transmits UL datathrough a predetermined resource, e.g. in a period of 100 sec, accordingto the corresponding SPS configuration.

In addition, S-SS id_net is a set of S-SS IDs selected from amongphysical layer SLSS IDs {0, 1, . . . , and 335}, used by terminals thathave selected the synchronization signal of the base station as asynchronization reference. S-SS id_net may be {0, 1, . . . , and 167}.In addition, S-SS id_oon is a set of S-SS IDs that terminals outside ofthe base station coverage use when directly transmitting asynchronization signal. S-SS id_oon may be {168, 169, . . . , and 335}.

As described above, resource allocation, time synchronization setting,reference signal transmission, and the like are performed independentlyor in concert with the base station in terminal-to-terminal sidelinkcommunication, unlike in related-art signal transmission and receptionbetween a base station and a terminal.

In particular, in the case of next-generation wireless access technology(including terms, such as NR and 5G), a plurality of protocols betweenthe base station and the terminal are added or modified. Accordingly, inNR technology-based sidelink communications, a variety of protocols arerequired to be newly developed, unlike related-artLTE-basedV2Xcommunication protocols.

The present disclosure is intended to propose operations, such as asynchronization signal receiving operation, resource allocation, andPSCCH, PSSCH, and DMRS configuration, in sidelink communicationsperformed between a transmitting terminal and a receiving terminal.Although embodiments will be described hereinafter with respect tosidelink communications, the embodiments may be equally applied toC-V2Xcommunications and D2Dcommunications, as described above.

In NR, in response to changes in the subcarrier spacing (SCS) in an OFDMsystem, changes in the frame structure of a sidelink to be used whentransmitting and receiving information in sidelink communications arealso required.

In a CP-OFDM waveform and a DFT-s-OFDM waveform, the sidelink signal inembodiments may use the CP-OFDM waveform. In addition, the sidelink mayuse SCS as follows. For example, in frequency range (FR) 1 using afrequency range of 6 GHz or lower, SCSs of 15 kHz, 30 kHz, and 60 kHzare used. Here, the sidelink may be configured to mainly use the 60 kHzspacing exhibiting best performance. In FR 2 using a frequency range of6 GHz or higher, 60 kHz and 120 kHz are used, and 60 kHz may mainly beused.

In addition, the sidelink uses a cyclic prefix (CP) in order to preventdemodulation that would otherwise occur during transmission andreception procedures in wireless communications. The length of the CPmay be set to be the same as the length of the normal CP of an NR Uuinterface. An extended CP may be used as required.

In this situation, the synchronization signal, resource allocation, andeach sidelink channel structure of the sidelink need to be configured inconsideration of efficiency.

Hereinafter, first, the configuration of a demodulation reference signal(DMRS) included in the PSSCH will be described.

FIG. 12 is a diagram illustrating operations of a transmitting terminalaccording to an embodiment.

Referring to FIG. 12, the transmitting terminal may perform an operationof receiving information regarding one or more DMRS patterns and aresource information set including information regarding one or moresidelink resources in S1200.

In the case of sidelink communication, two types of resource allocationmodes may be configured. For example, in Mode 1, the transmittingterminal requests sidelink wireless resource allocation from the basestation and performs sidelink communication using a sidelink wirelessresource allocated by the base station. In Mode 2, the base stationallocates a resource information set, i.e. information regarding one ormore sidelink wireless resources, to the sidelink terminal in advance,and the terminal performs sidelink communication by selecting a sidelinkwireless resource from the allocated resource information set. Althoughthe operations will be described as being set to Mode 2 in FIG. 12, thepresent disclosure is not limited thereto.

The resource information set and the information regarding one or moreDMRS patterns may be received by higher layer signaling. For example,the transmitting terminal or a receiving terminal located inside thecoverage of the base station receives the resource information setincluding one or more sidelink resources, to be used in sidelinkcommunication, by RRC signaling. In addition, at least one of thetransmitting terminal and the receiving terminal may receive theinformation regarding one or more DMRS patterns for sidelinkcommunication from the base station. The transmitting terminal and the

receiving terminal may respectively configure the resource informationset and DMRS pattern information therein by receiving the sameinformation.

In addition, the information regarding one or more DMRS patterns may bemapped according to the resource information set or the sidelinkresources. For example, when a first resource information set includingone or more pieces of resource information and a second resourceinformation set including one or more pieces of resource information areindicated by the base station, information regarding a single first DMRSpattern for the first resource information set and information regardinga single second DMRS pattern for the second resource information set maybe indicated by being mapped to the resource information set.Alternatively, the DMRS pattern information may be indicated by beingmapped according to respective sidelink resources included in a singleresource information set. Alternatively, the DMRS pattern informationmay be indicated by being mapped according to two or more sidelinkresource sub-sets included in a single resource information set.Alternatively, the DMRS pattern information may be indicated by beingmapped to respective groups obtained by grouping two or more resourceinformation sets. In addition, the sidelink resources and the DMRSpatterns may be indicated by being mapped in a variety of forms.

The transmitting terminal configures the received resource informationsets and the received DMRS patterns therein.

In S1210, the transmitting terminal may perform an operation ofselecting a single sidelink resource, via which sidelink communicationis performed, on the basis of the resource information set.

When sidelink communication is triggered, the transmitting terminalselects a predetermined sidelink resource from the configured resourceinformation set. A method by which the terminal selects thepredetermined sidelink resource from the configured resource informationset for sidelink communication may be performed according to a varietyof standards. For example, the transmitting terminal may select thepredetermined sidelink resource according to priorities allocated to aplurality of sidelink resources. Alternatively, the terminal may detectwhether or not each of the plurality of sidelink resources is used andselect a sidelink resource having a detection result value equal to orsmaller than a reference value. That is, the transmitting terminal mayselect a sidelink resource to use by detecting sidelink resources, eachof which is not used or is used less.

In S1220, the transmitting terminal may perform an operation ofselecting a predetermined DMRS pattern from the information regardingone or more DMRS patterns on the basis of the selected sidelinkresource.

For example, when a single sidelink resource is selected, thetransmitting terminal may select a DMRS pattern configured by beingmapped to the selected sidelink resource. Alternatively, thetransmitting terminal may select the DMRS pattern on the basis ofproperty information of the selected sidelink resource.

For example, the selected predetermined DMRS pattern may be determinedon the basis of information regarding consecutive symbols of a sidelinkresource selected for transmission of a physical sidelink shared channel(PSSCH), information regarding the number of symbols to which a physicalsidelink control channel (PSCCH) is allocated, and information regardingthe number of symbols of a DMRS included in the PSSCH. Specifically,when a PSSCH sidelink resource, via which sidelink data is to betransmitted, is selected, information regarding consecutive symbols ofthe corresponding PSSCH sidelink resource, the number of symbols of thePSCCH allocated in a slot in which the PSSCH is transmitted, and thenumber of DMRS symbols may be determined. In this case, the position ofa symbol, through which the DMRS is to be transmitted, may be determinedaccording to combinations of respective situations, on the basis ofpreviously-configured information in the form of a table. This will bedescribed in more detail hereinafter with reference to the accompanyingdrawings.

For example, the information regarding the number of symbols to whichthe PSCCH is allocated may be set to be 2 or 3, and the informationregarding the number of symbols of the DMRS included in the PSSCH may beset to be 2, 3, or 4. That is, respective construction factors may bedetermined for the respective sidelink resources in the above-describednumber range.

In S1230, the transmitting terminal may perform an operation oftransmitting the PSCCH and the PSSCH in a single slot using the selectedsidelink resource and transmitting the DMRS in a predetermined symbol ofthe PSSCH on the basis of the predetermined DMRS pattern in S1230.

For example, when the sidelink resource for the transmission of thesidelink data is determined, the transmitting terminal may transmit thePSCCH and the PSSCH in a single slot. The DMRS pattern informationincluded in the PSSCH may be indicated to the receiving terminal assidelink control information (SCI).

For example, predetermined DMRS pattern information applied to the PSSCHmay be indicated by a DMRS pattern filed of the SCI included in thePSCCH. The DMRS pattern filed may be included in first SCI and bedetermined to be one value from among 1 to 5 bits. Alternatively, thebit value of the DMRS pattern filed may be determined depending on anumber value of the DMRS pattern information transmitted by the basestation. An SCI format including a DMRS pattern indicator field is SCI0_1.

The receiving terminal may receive the sidelink data in the PSSCHsidelink resource indicated by the PSCCH and review DMRS symbolsallocated in the PSSCH region using the DMRS pattern indicator field.

According to the above-described operations, the transmitting terminalmay dynamically configure and transmit the DMRS pattern, and thereceiving terminal may receive the PSSCH by reviewing thedynamically-configured DMRS pattern.

FIG. 13 is a diagram illustrating operations of a receiving terminalaccording to an embodiment.

Referring to FIG. 13, in a method of performing sidelink communications,the receiving terminal may perform an operation of receiving informationregarding one or more DMRS patterns and a resource information setincluding information regarding one or more sidelink resources from thebase station in S1300.

The resource information set and the information regarding one or moreDMRS patterns may be received by higher layer signaling. For example,the transmitting terminal or the receiving terminal located inside thecoverage of the base station receives the resource information setincluding one or more sidelink resources, to be used for sidelinkcommunication, by RRC signaling. In addition, at least one of thetransmitting terminal and the receiving terminal may receive theinformation regarding one or more DMRS patterns for sidelinkcommunication from the base station. The transmitting terminal and thereceiving terminal may respectively configure the resource informationset and the DMRS pattern information therein by receiving the sameinformation.

In addition, the information regarding one or more DMRS patterns may bemapped according to the resource information set or sidelink resource.For example, when a first resource information set including one or morepieces of resource information and a second resource information setincluding one or more pieces of resource information are indicated bythe base station, information regarding a single first DMRS pattern forthe first resource information set and information regarding a singlesecond DMRS pattern for the second resource information set may beindicated by being mapped to the resource information set.Alternatively, the DMRS pattern information may be indicated by beingmapped according to respective sidelink resources included in a singleresource information set. Alternatively, the DMRS pattern informationmay be indicated by being mapped according to two or more sidelinkresource sub-sets included in a single resource information set.Alternatively, the DMRS pattern information may be indicated by beingmapped to respective groups obtained by grouping two or more resourceinformation sets. In addition, the sidelink resources and the DMRSpatterns may be indicated by being mapped in a variety of forms.

In S1310, the receiving terminal may perform an operation of receivingthe PSCCH via a single sidelink resource selected by the transmittingterminal.

When the transmitting terminal transmits a sidelink signal by a Mode 2resource allocation method, the receiving terminal may receive the PSCCHvia a single sidelink resource included in the resource information set.Alternatively, the PSCCH may be received via the sidelink resourceconfigured as being default or configured as being dedicated to thesidelink.

In S1320, the receiving terminal may perform an operation of reviewingscheduling information of the PSSCH and predetermined DMRS patterninformation, received as being included in the PSSCH, on the basis ofPSCCH.

The PSCCH includes sidelink control information (SCI). The SCI mayinclude scheduling information for the PSSCH. The scheduling informationmay include information indicating frequency and time domain resourcesfor the reception of the PSSCH. In addition, as described above, the SCImay include a DMRS pattern indicator field indicating informationregarding a DMRS pattern applied to the PSSCH. That is, the receivingterminal may review the DMRS pattern information, selected by thetransmitting terminal, through the PSCCH.

In S1330, the receiving terminal may perform an operation of receiving aDMRS in a predetermined symbol of the PSSCH on the basis ofpredetermined DMRS pattern information.

For example, the predetermined DMRS pattern information may be indicatedby the DMRS pattern filed of the SCI included in the PSCCH.

In addition, the selected predetermined DMRS pattern may be determinedon the basis of information regarding consecutive symbols of thesidelink resource selected for the transmission of a PSSCH, informationregarding the number of symbols to which a PSCCH is allocated, andinformation regarding the number of symbols of the DMRS included in thePSSCH. Specifically, when a PSSCH sidelink resource, via which sidelinkdata is to be transmitted, is selected, information regardingconsecutive symbols of the corresponding PSSCH sidelink resource, thenumber of symbols of the PSCCH allocated in a slot in which the PSSCH istransmitted, and the number of DMRS symbols may be determined. In thiscase, the position of a symbol, through which the DMRS is to betransmitted, may be determined according to combinations of respectivesituations, on the basis of previously-configured information in theform of a table. The transmitting terminal may select the predeterminedDMRS pattern through the above-described operations, and the receivingterminal may review the same according to the corresponding DMRS patterninformation.

For example, the information regarding the number of symbols to whichthe PSCCH is allocated may be set to be 2 or 3, and the informationregarding the number of symbols of the DMRS included in the PSSCH may beset to be 2, 3, or 4. That is, respective construction factors may bedetermined for the respective sidelink resources in the above-describednumber range.

For example, the DMRS pattern filed may be included in first SCI and bedetermined to be one value from among 1 to 5 bits. Alternatively, thebit value of the DMRS pattern filed may be determined depending on anumber value of the DMRS pattern information transmitted by the basestation. An SCI format including a DMRS pattern indicator field is SCI0_1.

According to the above-described operations, even when the DMRS patternin the PSSCH is dynamically changed, the receiving terminal may receivethe PSSCH by reviewing the dynamically-changed DMRS pattern.

Hereinafter, a variety of embodiments configuring a DMRS pattern andsharing configuration information in performing sidelink communicationsthat the transmitting terminal and the receiver described above mayperform will be described with reference to the accompanying drawings.

FIG. 14 is a diagram illustrating sidelink control information fieldsaccording to an embodiment.

Referring to FIG. 14, a transmitting terminal may transmit a PSCCHincluding sidelink control information (SCI) to a receiving terminal.The SCI may be included in each of the PSCCH and the PSSCH. The SCItransferred by being included in the PSCCH will be described as firstSCI or stage 1 SCI, while the SCI transferred by being included in thePSSCH will be described as second SCI or stage 2 SCI.

The first SCI and the second SCI include different SCI. FIG. 14illustrates example fields of the first SCI.

For example, the first SCI includes a priority field regarding priority,a frequency resource allocation (or assignment) field regarding thePSSCH, and a time resource allocation (or assignment) field. In case ofresource reservation, resource reservation period information isincluded. In addition, the first SCI may include the above-describedDMRS pattern indicator field. In addition, the first SCI may include aformat field indicating a second SCI format, a beta offset indicatorfield, a field indicating the number of DMRS ports, and a fieldindicating modulation and a coding scheme.

Among these, the size of the frequency and resource reservation periodfield may be variably set. A DMRS pattern field and a second SCI formatfield may be fixed to predetermined bits or may be variably configured.

The receiving terminal may review the DMRS pattern information byreceiving the first SCI illustrated in FIG. 14.

FIG. 15 is a diagram illustrating a pattern in which a PSCCH and a PSSCHare assigned to a single slot and a DMRS is allocated to a variety ofsymbols.

Referring to FIG. 15, 14 symbols may be provided in a single sidelinkslot. In this case, the PSCCH may be comprised of three symbol regions 0to 2. Alternatively, the PSCCH may be comprised of two symbol regionswith indices 0 and 1. Symbols in the remaining slots except for thePSCCH are allocated to the PSSCH region. The DMRS may be transmitted insome symbols in the PSSCH region.

As described above, DMRS time domain positions are determined by DMRSpattern information. As illustrated in FIG. 15, the number of symbols,to which the DMRS is allocated, included in a single slot may bevariably determined.

In addition, in a case in which the slot is comprised of 14 symbols, apattern in which the DMRS is allocated to the same positions of symbolshaving symbol indices 0 to 6 and symbols having symbol indices 7 to 13may be configured. Alternatively, symbols to which the DMRS is allocatedmay be determined to be symmetrical about the boundary between symbolindices 6 and 7 or to be asymmetrical.

The allocation pattern of the frequency domain of the DMRS will bedescribed as follows.

FIGS. 16 to 19 are diagrams illustrating patterns in a variety offrequency domain in which a DMRS is disposed in a predetermined symbolof a PSSCH according to a DMRS pattern.

Referring to FIG. 16, the DMRS may be allocated to all subcarriers ofallocated symbols. For example, when two DMRS symbols are allocated in asingle slot, the DMRS may be allocated to all subcarriers of thecorresponding symbols.

In addition, referring to FIG. 17, the DMRS may be allocated to somesubcarriers of allocated symbols. For example, when two DMRS symbols ina single slot are allocated, the DMRS may be allocated to somesubcarriers of each of the symbols. A predetermined number ofconsecutive subcarriers to which the DMRS is allocated and anothernumber of subcarriers to which the DMRS is not allocated may berepeated.

In addition, referring to FIG. 18, the DMRS may be allocated to somesubcarriers of allocated symbols. For example, when two DMRS symbols ina single slot are allocated, the DMRS may be allocated with one offset.In this case, a frequency domain DMRS pattern of Comb 1 may beconfigured. FIG. 19 illustrates a frequency domain DMRS patternconfigured to be Comb 2.

In addition, the DMRS pattern may be dynamically configured according tothe speed of the sidelink terminal in a single slot. For example, withincreases in the speed of the sidelink terminal, the number of symbolsto which the DMRS is allocated may be increased or reduced in a singleslot.

As described above, one or more DMRS patterns may be mapped in eachresource information set. In this case, the transmitting terminal mayselect resource information for transmission of a sidelink signal, andreview an select a DMRS pattern mapped to the resource information. Thiswill be described in more detail with reference to FIG. 20.

FIG. 20 is a diagram illustrating a method of determining DMRSallocation symbols according to an embodiment.

Referring to FIG. 20, a DMRS pattern applied to a PSSCH may bedetermined on the basis of information regarding consecutive symbols ofa sidelink resource selected for PSSCH transmission by the transmittingterminal, information regarding the number of symbols to which a PSCCHis allocated, and information regarding the number of symbols of theDMRS included in the PSSCH.

For example, the consecutive symbol information Ld of the sidelinkresource selected for PSSCH transmission by the transmitting terminalmay be selected to be one from among 6 to 13. The information regardingthe number of symbols to which the PSCCH is allocated may be set to be 2or 3, while the information regarding the number of symbols of the DMRSincluded in the PSSCH may be set to be 2, 3, or 4.

In a case in which the transmitting terminal configures the tableillustrated in FIG. 20, the number of consecutive symbols of thesidelink resource selected for PSSCH transmission is 10, and two PSCCHsymbols are allocated in the corresponding slot, a symbol index L may beappreciated for each of cases in which the numbers of DMRS symbols are2, 3, and 4. That is, when two DMRS symbols are allocated in a singleslot, the DMRS is allocated symbol indices 3 and 8. When three DMRSsymbols are allocated in a single slot, the DMRS may be allocated symbolindices 1, 4, and 7. Here, symbol indices may refer to indices allocatedto 0 to 13 with respect to the slot. Alternatively, symbol indices mayrefer to allocated indices, except for symbols in the PSCCH region.

Thus, when the table of FIG. 20 is configured in the transmittingterminal and the receiving terminal in this manner, the DMRS patterninformation included in the DMRS pattern indicator field may onlyinclude information indicating the number of DMRSs allocated to thePSSCH. That is, since the number of consecutive symbols of the PSSCH andthe number of symbols configured with the PSCCH may be reviewed viaother fields of sidelink control information (SCI), when the DMRS numberinformation is reviewed, the receiving terminal may review informationregarding the symbols, to which the DMRS is allocated, using the table.In this case, the DMRS indicator field may be comprised of 2 bits.

In addition, the DMRS pattern indicator field may be comprised of twosubfields. For example, the DMRS pattern indicator field is comprised ofsubfield A and subfield B, in which field A includes informationindicating SCS information of the PSSCH (e.g. 15 kHz: 00, 30 kHz: 01, 60kHz: 10, and 120 kHz: 11). Field B may include pattern informationindicating symbols to which the DMRS is allocated in order to solve asynchronization problem according to the movement speed of the terminalin the SCS determined by field A. For example, field B may be comprisedof three bits (e.g. 1:000, 2:001, 3:010, 4:011, and 5:100).

According to the above-described operations, the transmitting terminaland the receiving terminal may communicate with each other by reviewingthe DMRS information in the sidelink channel.

In addition, operations of transmitting and receiving a synchronizationsignal to perform sidelink communication in a case in whichsynchronization configuration based on the base station is applied willbe described.

In sidelink communication, an allocated frequency range may be set to berelatively narrow in a number of cases, unlike the case of the Uuinterface. There may be more cases in which information must betransmitted through a broadcast channel. In addition, slot-basedtransmission of the synchronization signal is required.

Thus, the present disclosure proposes a sidelink synchronization signalblock different from the synchronization signal block (SSB) in the Uuinterface.

The terminal may perform an operation of receiving the configurationinformation of the SSB including synchronization information forsidelink communication.

For example, the sidelink synchronization signal block configurationinformation may include at least one from among subcarrier indexinformation of a frequency domain in which the sidelink synchronizationsignal block is transmitted, information regarding the number ofsidelink synchronization signal blocks transmitted within a singlesidelink synchronization signal period, offset information from a startpoint of the sidelink synchronization signal period to a first sidelinksynchronization signal block monitoring slot, and interval informationbetween sidelink synchronization signal block monitoring slots. In anexample, the period of the sidelink synchronization signal may beconfigured to be 16 frames and to be 160 ms. In another example, theperiod of the sidelink synchronization signal may be configured to be 16multiples.

In another example, the number of sidelink synchronization signal blocksmay be set to be within a differential range according to the subcarrierspacing set to a frequency range in which the sidelink synchronizationsignal block is transmitted. The subcarrier spacing in the frequencyrange may be configured to be 15, 30, 60, 120, and 240 kHz, asillustrated in Table 1. Specifically, when the subcarrier spacing is 15kHz, the number of sidelink synchronization signal blocks is set to be 1or 2. Alternatively, when the subcarrier spacing is 30 kHz, the numberof sidelink synchronization signal block is set to be 1, 2, or 4.Alternatively, when the subcarrier spacing is 60 kHz, the number ofsidelink synchronization signal block is set to be one from among 1, 2,4, and 8. Alternatively, when the subcarrier spacing is 120 kHz, thenumber of sidelink synchronization signal block is set to be one fromamong 1, 2, 4, 8, 16, 32, and 64. In addition, in the case of FR2,evenwhen the subcarrier spacing is set to be 60 kHz, the number of sidelinksynchronization signal blocks may be set to be one from among 1, 2, 4,8, 16, and 32.

The terminal may perform an operation of monitoring a configuredsidelink synchronization signal block monitoring slot on the basis ofthe sidelink synchronization signal block configuration information. Forexample, the terminal monitors a predetermined slot in the period of thesidelink synchronization signal on the basis of the sidelinksynchronization signal block configuration information.

For example, when 16 frames are configured in a period of the sidelinksynchronization signal, the spacing from a start slot of the period ofthe sidelink synchronization signal to a first sidelink synchronizationsignal block monitoring slot of the period of the synchronization signalis reviewed, on the basis of the offset information. In addition, theterminal reviews the spacing from the first sidelink synchronizationsignal block monitoring slot to a second sidelink synchronization signalblock monitoring slot using the interval information. In the samemanner, the spacing from the second sidelink synchronization signalblock monitoring slot to a third sidelink synchronization signal blockmonitoring slot is reviewed using the interval information. In addition,the terminal counts the number of the entire sidelink synchronizationsignal block monitoring slots allocated in the period of the sidelinksynchronization signal using the information regarding the number of thesidelink synchronization signal blocks. Thus, the terminal reviews andmonitors the index (or position) of the monitoring slot in the period ofthe sidelink synchronization signal using the sidelink synchronizationsignal block configuration information.

The terminal may perform an operation of receiving the sidelinksynchronization signal block in the sidelink synchronization signalblock monitoring slot. For example, the terminal receives the sidelinksynchronization signal block in the monitoring slot using theabove-described sidelink synchronization signal block configurationinformation. The sidelink synchronization signal block is comprised of asidelink primary synchronization signal (S-PSS), a sidelink secondarysynchronization signal (S-SSS), and a physical sidelink broadcastchannel (PSBCH). The S-PSS, the S-SSS, and the PSBCH may be allocated toN number of consecutive symbols in the sidelink synchronization signalblock monitoring slot.

The sidelink synchronization signal block may be allocated to N numberof consecutive symbols in the sidelink synchronization signal blockmonitoring slot. In this case, the sidelink synchronization signal blockmay be comprised of two S-PSSs, two S-SSSs, and N-4 number of PSBCHsymbols. For example, the sidelink synchronization signal block may beallocated with the PSBCH at symbol index 0 in the sidelinksynchronization signal block monitoring slot. In addition, the sidelinksynchronization signal block may be allocated with the S-PSS at symbolindices 1 and 2, the S-SSS at symbol indices 3 and 4, and the PSBCH atsymbol indices 5 to N-1. In this case, when the sidelink synchronizationsignal block monitoring slot is a normal cyclic prefix (CP), N is 13.When the sidelink synchronization signal block monitoring slot is anextended CP, N is 11. That is, when a single slot is comprised of 14 or12 symbols, the sidelink synchronization signal block may be configuredby excluding the last symbol and allocating the S-PSS, the S-SSS, andthe PSBCH. In another example, the sidelink synchronization signal blockmay be comprised of 132 subcarriers.

In addition, also in sidelink communication, an HARQ operation may beperformed. However, there is a problem in that the HARQ operationfrequently performed in sidelink communications causes the overlappingof resources and increased system load. In addition, the HARQ operationmay not be properly performed due to the limited transmission power ofthe terminal.

Therefore, hereinafter, an HARQ operation of the terminal will beproposed.

In a method of controlling a sidelink HARQ feedback operation, theterminal may perform an operation of receiving group-cast sidelink datafrom the transmitting terminal through the physical sidelink sharedchannel (PSSCH). For example, the terminal receives the PSCCH and thePSSCH from the transmitting terminal. Sidelink communication may supportunicast communication between terminals, groupcast communication betweena single transmitting terminal and plurality of receiving terminals in agroup, and broadcast communication in which a single transmittingterminal performs broadcasting. In the case of groupcast communication,the PSCCH may include scheduling information regarding a PSSCH wirelessresource including sidelink groupcast data. The terminal receives thePSSCH including groupcast sidelink data on the basis of the SCI includedin the PSCCH.

The terminal may perform an operation of determining whether or not totransmit HARQ feedback information of the groupcast sidelink data on thebasis of position information of the transmitting terminal. For example,the position information of the transmitting terminal may be included insidelink control information (SCI) received through the PSSCH andinclude zone ID information of the transmitting terminal. The SCIreceived through the PSSCH may mean second SCI. That is, the SCIreceived through the PSSCH is separated from the SCI including thescheduling information regarding the groupcast sidelink data andreceived through the PSCCH. For example, the SCI received through thePSSCH may include HARQ process ID information, new data commandinformation, redundancy version information, transmitting terminal IDinformation, receiving terminal ID information, CSI request information,zone ID information, and communication range request information. Inaddition, geographic position information mapped according to the zoneID information may be received from the base station by higher layersignaling. The terminal may obtain the position information of thetransmitting terminal using the geographic position informationaccording to the zone ID information received from the base station andthe zone ID information of the transmitting terminal.

In addition, the HARQ feedback information may be determined on thebasis of information regarding a distance calculated according to theposition of the transmitting terminal and the position of the terminaland whether or not the decoding of the groupcast sidelink data hassucceeded. In an example, only when the decoding of the groupcastsidelink data has failed and the distance information is equal to orless than a predetermined threshold value, it may be determined totransmit the HARQ feedback information. Here, the HARQ feedbackinformation may include HARQ-NACK information. In another example, whenthe distance information is equal to or greater than the predeterminedthreshold value, it may be determined to transmit the HARQ feedbackinformation including HARQ-ACK or HARQ-NACK information depending onwhether or not the decoding of the groupcast sidelink data hassucceeded. In a further example, when the decoding of the groupcastsidelink data has succeeded, it may be determined not to transmit theHARQ feedback information irrespective of the distance information. Inyet another example, only when the decoding of the groupcast sidelinkdata has failed, it may be determined whether or not to transmit theHARQ feedback information on the basis of the distance information.

The above-described transmission of the HARQ feedback information may beonly performed when the sidelink HARQ feedback operation is activated.That is, the sidelink HARQ feedback operation may be activated ordeactivated, and whether to activate or deactivate the sidelink HARQfeedback operation may be determined by a command from the base stationor the transmitting terminal. In addition, the above-described thresholdvalue may be included in the SCI received through the PSSCH (as, forexample, communication range request information) or may be provided inthe terminal by the base station.

When it is determined to transmit the HARQ feedback information, theterminal may perform an operation of transmitting the HARQ feedbackinformation. For example, when it is determined to transmit the HARQfeedback information, the terminal may transmit the HARQ feedbackinformation regarding the groupcast sidelink data.

The above-described operations provide effects that unnecessary sidelinksystem load may be reduced and the HARQ feedback operation based on thedistance information between the transmitting terminal and the terminalmay be performed.

FIG. 21 is a diagram illustrating a configuration of a transmittingterminal according to an embodiment.

Referring to FIG. 21, a transmitting terminal 2100 may include areceiver 2130, a controller 2110, and a transmitter 2120. The receiver2130 receives information regarding one or more DMRS patterns and aresource information set including information regarding one or moresidelink resources from a base station. The controller 2110 selects asingle sidelink resource, via which sidelink communication is to beperformed, on the basis of the resource information set, and selects apredetermined DMRS pattern from the information regarding one or moreDMRS patterns, on the basis of the selected sidelink resource. Thetransmitter 2120 transmits a PSCCH and a PSSCH in a single slot usingthe selected sidelink resource, and transmits a DMRS in a predeterminedsymbol of the PSSCH on the basis of the predetermined DMRS pattern.

The receiver 2130 may include the resource information set and theinformation regarding one or more DMRS patterns by higher layersignaling. For example, the transmitting terminal 2100 or a receivingterminal located in the coverage of the base station receives theresource information set including one or more sidelink resources, to beused in sidelink communication, by RRC signaling. In addition, at leastone of the transmitting terminal 2100 and the receiving terminal mayreceive the information regarding one or more DMRS patterns for sidelinkcommunication from the base station. The transmitting terminal 2100 andthe receiving terminal may configure the resource information set andthe DMRS pattern information therein by receiving the same information.

In addition, the information regarding one or more DMRS patterns may bemapped according to the resource information set or the sidelinkresources. For example, when a first resource information set includingone or more pieces of resource information and a second resourceinformation set including one or more pieces of resource information areindicated by the base station, information regarding a single first DMRSpattern for the first resource information set and information regardinga single second DMRS pattern for the second resource information set maybe indicated by being mapped to the resource information set.Alternatively, the DMRS pattern information may be indicated by beingmapped according to respective sidelink resources included in a singleresource information set. Alternatively, the DMRS pattern informationmay be indicated by being mapped according to two or more sidelinkresource sub-sets included in a single resource information set.Alternatively, the DMRS pattern information may be indicated by beingmapped to respective groups obtained by grouping two or more resourceinformation sets. In addition, the sidelink resources and the DMRSpatterns may be indicated by being mapped in a variety of forms. Thecontroller 2110 configures the received resource information set and thereceived DMRS pattern in the terminal.

When sidelink communication is triggered, the controller 2110 selects apredetermined sidelink resource from the configured resource informationset. A method by which the controller 2110 selects the predeterminedsidelink resource from the configured resource information set forsidelink communication may be performed according to a variety ofstandards. For example, the controller 2110 may select the predeterminedsidelink resource according to priorities allocated to a plurality ofsidelink resources. Alternatively, the controller 2110 may detectwhether or not each of the plurality of sidelink resources is used andselect a sidelink resource having a detection result value equal to orsmaller than a reference value. That is, the controller 2110 may selecta sidelink resource to use by detecting sidelink resources, each ofwhich is not used or is used less.

In addition, when a single sidelink resource is selected, the controller2110 may select a DMRS pattern configured by being mapped to theselected sidelink resource. Alternatively, the controller 2110 mayselect the DMRS pattern on the basis of property information of theselected sidelink resource.

For example, the selected predetermined DMRS pattern may be determinedon the basis of information regarding consecutive symbols of a sidelinkresource selected for transmission of a physical sidelink shared channel(PSSCH), information regarding the number of symbols to which a physicalsidelink control channel (PSCCH) is allocated, and information regardingthe number of symbols of a DMRS included in the PSSCH. Specifically,when a PSSCH sidelink resource, via which sidelink data is to betransmitted, is selected, information regarding consecutive symbols ofthe corresponding PSSCH sidelink resource, the number of symbols of thePSCCH allocated in a slot in which the PSSCH is transmitted, and thenumber of DMRS symbols may be determined. In this case, the position ofa symbol, through which the DMRS is to be transmitted, may be determinedaccording to combinations of respective situations, on the basis ofpreviously-configured information in the form of a table.

For example, the information regarding the number of symbols to whichthe PSCCH is allocated may be set to be 2 or 3, and the informationregarding the number of symbols of the DMRS included in the PSSCH may beset to be 2, 3, or 4. That is, respective construction factors may bedetermined for the respective sidelink resources in the above-describednumber range. In this case, the controller 2110 may control the DMRSpattern to be indicated to the receiving terminal by setting the DMRSpattern indicator field to only include the information regarding thenumber of PSSCH DMRS symbols.

In addition, the controller 2110 may control the operation of thetransmitting terminal 2110 required for performing the foregoingembodiments.

In addition, the transmitter 2120 and the receiver 2130 serve totransmit and receive signals, data, and messages to and from the basestation and the receiving terminal through the corresponding channels.

Embodiments of the present disclosure may be supported by standarddocuments of at least one of the IEEE 802 system, the 3GPP system, andthe 3GPP2 system, all of which are wireless access systems. That is,steps, components, or portions not described in embodiments of thepresent disclosure for the sake of clearly describing the spirit of thepresent disclosure may be supported by the standard documents. For allterms used herein, reference may be made to the standard documents.

Embodiments of the present disclosure may be implemented using a varietyof means. For example, embodiments of the present disclosure may beimplemented using hardware, firmware, software, or any combinationthereof.

In the case in which the present disclosure is implemented usinghardware, the methods according to embodiments of the present disclosuremay be realized using one or more application specific integratedcircuits (ASICs), digital signal processors (DSPs), digital signalprocessing devices (DSPDs), programmable logic devices (PLDs), fieldprogrammable gate arrays (FPGAs), processors, controllers,microcontrollers, microprocessors, or the like.

In the case in which the present disclosure is implemented usingfirmware or software, the methods according to embodiments of thepresent disclosure may be implemented in the form of devices, processes,functions, or the like performing the functions or operations describedabove. Software codes may be stored in a memory unit so as to beexecuted by a processor. The memory unit may be located inside oroutside of the processor and may exchange data with the processor via avariety of known means.

The terms, such as “system”, “processor”, “controller”, “component”,“module”, “interface”, “model”, or “unit”, used herein may generallyrefer to computer-related entity hardware, a combination of hardware andsoftware, software, or software in execution. For example, theabove-described components may be at least one selected from among, butnot limited to, a process, a processor, a controller, a controlprocessor, an entity, an execution thread, a program, and a computer.For example, both an application being executed by the controller orprocessor and the controller or processor may be a component. One ormore components may reside in at least one of a process and an executionthread. A component may be located in a single device (e.g. a system ora computing device) or may be distributed between two or more devices.

The foregoing descriptions have been presented in order to explaincertain principles of the present disclosure by way of example. Thosehaving ordinary knowledge in the technical field to which the presentdisclosure relates could make various modifications and variationswithout departing from the essential features of the principle of thepresent disclosure. In addition, the foregoing embodiments shall beinterpreted as being illustrative, while not being limitative, of theprinciple and scope of the present disclosure. It should be understoodthat the scope of protection of the present disclosure shall be definedby the appended Claims and all of their equivalents fall within thescope of protection of the present disclosure.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority under 35 U.S.C. § 119 (a) of the UnitedStates Patent Act to Korean Patent Application Nos. 10-2019-0043200,filed on Apr. 12, 2019, 10-2019-0043283, filed on Apr. 12, 2019, and10-2019-0077361, filed on Jun. 27, 2019, 10-2019-0156725, filed on Nov.29, 2019, 10-2020-0042169, filed on Apr. 7, 2020, all of which arehereby incorporated by reference for all purposes as if fully set forthherein. In addition, when this application also claims priority forcountries other than the United States for the same reason as above, allof the contents of the above-listed applications are hereby incorporatedby reference.

1. A method of performing sidelink communication by a transmittingterminal, the method comprising: receiving information regarding one ormore DMRS patterns and a resource information set including informationregarding one or more sidelink resources from a base station; selectinga single sidelink resource for performing sidelink communication inaccordance with the resource information set; selecting a predeterminedDMRS pattern from the information regarding one or more DMRS patterns inaccordance with the selected sidelink resource; and transmitting a PSCCHand a PSSCH in a single slot using the selected sidelink resource andtransmitting a DMRS in a predetermined symbol of the PSSCH in accordancewith the predetermined DMRS pattern.
 2. The method according to claim 1,wherein the information regarding one or more DMRS patterns and theresource information set are received by higher layer signaling, and theinformation regarding one or more DMRS patterns is mapped according tothe resource information set or the sidelink resources.
 3. The methodaccording to claim 1, wherein information regarding the predeterminedDMRS pattern is indicated by a DMRS pattern filed of the sidelinkcontrol information included in the PSCCH.
 4. The method according toclaim 1, wherein the predetermined DMRS pattern is determined inaccordance with information regarding consecutive symbols of a sidelinkresource selected for transmission of the PSSCH, information regardingthe number of symbols to which the PSCCH is allocated, and informationregarding the number of symbols of a DMRS included in the PSSCH.
 5. Themethod according to claim 4, wherein the information regarding thenumber of symbols to which the PSCCH is allocated is 2 or 3, and theinformation regarding the number of symbols of the DMRS included in thePSSCH is set to be 2, 3, or
 4. 6. A method of performing sidelinkcommunication by a receiving terminal, the method comprising: receivinginformation regarding one or more DMRS patterns and a resourceinformation set including information regarding one or more sidelinkresources from a base station; receiving a PSCCH via a single sidelinkresource selected by a transmitting terminal; reviewing schedulinginformation of a PSSCH and information regarding a predetermined DMRSpattern received by being included in the PSSCH, in accordance with thePSCCH; and receiving a DMRS in a predetermined symbol of the PSSCH inaccordance with the information regarding a predetermined DMRS pattern.7. The method according to claim 6, wherein the information regardingone or more DMRS patterns and the resource information set are receivedby higher layer signaling, and the information regarding one or moreDMRS patterns is mapped according to the resource information set or thesidelink resources.
 8. The method according to claim 6, wherein theinformation regarding a predetermined DMRS pattern is indicated by aDMRS pattern filed of the sidelink control information included in thePSCCH.
 9. The method according to claim 6, wherein the predeterminedDMRS pattern is determined in accordance with information regardingconsecutive symbols of a sidelink resource selected for transmission ofthe PSSCH, information regarding the number of symbols to which thePSCCH is allocated, and information regarding the number of symbols of aDMRS included in the PSSCH.
 10. The method according to claim 9, whereinthe information regarding the number of symbols to which the PSCCH isallocated is 2 or 3, and the information regarding the number of symbolsof the DMRS included in the PSSCH is set to be 2, 3, or
 4. 11. Atransmitting terminal performing sidelink communication, thetransmitting terminal comprising: a receiver receiving informationregarding one or more DMRS patterns and a resource information setincluding information regarding one or more sidelink resources from abase station; a controller selecting a single sidelink resource forperforming sidelink communication in accordance with the resourceinformation set and selecting a predetermined DMRS pattern from theinformation regarding one or more DMRS patterns in accordance with theselected sidelink resource; and a transmitter transmitting a PSCCH and aPSSCH in a single slot using the selected sidelink resource andtransmitting a DMRS in a predetermined symbol of the PSSCH in accordancewith the predetermined DMRS pattern.
 12. The transmitting terminalaccording to claim 11, wherein the information regarding one or moreDMRS patterns and the resource information set are received by higherlayer signaling, and the information regarding one or more DMRS patternsis mapped according to the resource information set or the sidelinkresources.
 13. The transmitting terminal according to claim 11, whereininformation regarding the predetermined DMRS pattern is indicated by aDMRS pattern filed of the sidelink control information included in thePSCCH.
 14. The transmitting terminal according to claim 11, wherein thepredetermined DMRS pattern is determined in accordance with informationregarding consecutive symbols of a sidelink resource selected fortransmission of the PSSCH, information regarding the number of symbolsto which the PSCCH is allocated, and information regarding the number ofsymbols of a DMRS included in the PSSCH.
 15. The transmitting terminalaccording to claim 14, wherein the information regarding the number ofsymbols to which the PSCCH is allocated is 2 or 3, and the informationregarding the number of symbols of the DMRS included in the PSSCH is setto be 2, 3, or 4.